This invention relates to an isolation device for providing optical and electrical isolation between areas of an integrated optical circuit.
It is known to isolate two optically conductive areas of an integrated optical circuit from each other by providing a trench between the two areas. If the trench is empty, optical isolation is provided by reflection of stray light at the interface between the optically conductive area and the trench. It is preferable instead to absorb the stray light by filling the trench with light absorbent material. However, this may have a tendency of reducing the electrical isolation between the two optically conductive areas.
It is also known to absorb stray light by providing dopant in selected areas of an optical chip, e.g. as described in WO-A-99/28772, the disclosure of which is incorporated herein.
This invention aims to provide an alternative form of device which provides both optical and electrical isolation.
According to the invention, there is provided an isolation device for providing optical and electrical isolation between areas of an integrated optical chip comprising a first elongate region doped with a first dopant material, a second elongate region on one side of the first elongate region and a third elongate region on the opposite side of the first elongate region, the second and third elongate regions being doped with a second dopant material of opposite polarity to the first dopant material so a first diode is formed between the second and first elongate regions and a second diode is formed between the first and third elongate regions, the first and second diodes being connected in series with opposing polarity.